1. Field of the Invention
The invention is related to the field of communications and, in particular, to charging for CAMEL services in an IMS network.
2. Statement of the Problem
First-generation (1G) wireless telephone technology provides standards for mobile communications using analog signals between a mobile device and a base station. Second-generation (2G) wireless telephone technology is a successor to the 1G standards. 2G technology provides standards for mobile communications using digital signals instead of analog signals between the mobile device and the base station. Some common 2G technologies are Global System for Mobile Communications (GSM), IS-95 (which is based on Code Division Multiple Access (CDMA), etc. 2G networks, such as a GSM network, typically provide intelligent network (IN) capabilities. Intelligent networks distribute the functionality of providing telephony services (e.g., call waiting, call forwarding, etc) among multiple intelligent networks. For instance, when a Mobile Switching Center (MSC) in a GSM network receives signaling for a call, the MSC processes service triggers to determine whether a service should be invoked. If a service trigger is detected, then the MSC interrupts call processing and routes the call to the proper intelligent network where the intelligent network provides the service for the call.
Customized Application of Mobile Enhanced Logic (CAMEL) is logic typically used in GSM networks to add new services to the network. CAMEL is defined in the 2G standards and is based on the concept of intelligent networks. CAMEL triggers are defined and accessible by the MSC of the network. When the MSC receives a call, the MSC processes the CAMEL triggers along with other triggers to determine whether a CAMEL service should be invoked. If a CAMEL trigger is detected, then the MSC interrupts call processing and transmits a CAMEL application protocol (CAP) message to the proper intelligent network (typically referred to as a GSM service control function (SCF)). Responsive to the CAP message, the GSM SCF provides the appropriate CAMEL service for the call. Exemplary CAMEL services include Calling Line Identification Presentation (CLIP), Calling Line Identification Restriction (CLIR), call forwarding, call holding, etc.
After the GSM SCF provides the CAMEL service for the call, the GSM SCF generates CAMEL charging data for the service, and transmits a CAP response to the MSC that includes the CAMEL charging data. After the call has ended, the MSC generates a Call Detail Record (CDR) and populates the fields of the CDR with charging data for the call. The 2G standards for the CDR define fields for the CAMEL charging data along with fields for other charging data for the call. The MSC then transmits the CDR to a billing system, and the billing system resolves the billing for the call.
A successor to the 2G wireless telephone technology is third-generation (3G) wireless telephone technology. The services associated with 3G provide the ability to simultaneously transfer both voice data (e.g., a telephone call) and non-voice data (e.g., downloading information, exchanging email, and instant messaging). One type of 3G communication network gaining popularity is an IP Multimedia Subsystem (IMS) network. As set forth in the 3rd Generation Partnership Project (3GPP) or 3GPP2, IMS provides a common core network having access-agnostic network architecture for converged networks. Service providers are accepting this architecture in next generation network evolution. The IMS architecture is initially defined by the 3GPP to provide multimedia services to mobile subscribers over an Internet Protocol (IP) network. IP networks have become the most cost savings bearer network to transmit video, voice, and data. IMS uses the advantage of IP networks to provide multimedia services for IMS subscribers on an IMS platform. The signaling used within IMS networks is Session Initiation Protocol (SIP). IMS defines the standard SIP interface between application servers, the IMS core network (CSCF), the IMS subscriber, the IMS database (HSS), and IMS billing elements. These standards can reduce the network integration costs and let the subscriber enjoy more stable services.
Network operators may want to implement CAMEL in IMS networks to provide CAMEL services. One problem with present IMS networks is that the IMS standards have not defined how charging is performed for CAMEL services that are provided by an IMS network. As a result, CAMEL services cannot be provided in IMS networks as there is no way to charge for the CAMEL services.